I'd say to leave it to a reputable mechanic if you can find one, or at least someone who knows their way around the bay of an E30. BMWs require some special tools, I'm not sure if the valvejob does or not, since I had mine done by my mechanic. If you do it yourself without much knowledge of what you're doing, any minimal maladjustment can leave you with bent stems, cracked heads, or all kinds of nasty garbage.
Too scary a risk to be taken in one's own driveway.
But if you're really confident about your mechanical skills, that's up to you.